1. Field of the Invention
The present invention relates to a thin motor-driven centrifugal blowing fan apparatus. More particularly it relates to a structure of a blade assembly thereof, which is arranged to draw in air from the direction of the rotation axis and to discharge the air perpendicular to the rotation axis.
2. Description of the Related Art
From the viewpoint of the shape of blades for drawing in and blowing air, structures of blade assemblies of conventional thin motor-driven centrifugal blowing fan apparatuses may be classified into axial fan blade types and centrifugal fan blade types.
In the axial fan blade type, when the space between an inlet and a blade is insufficient, significant air backflow occurs. This makes the operation of drawing in air ineffective, lowering efficiency and, increasing the noise level. This limits applicability of the fan apparatus as it is impossible to use it in areas such as the interiors of electronic and electric devices requiring miniaturization. On the other hand, in the centrifugal fan blade type, air flows along the blades, and the volume of air to be drawn in is determined by the height of the blades. Therefore, the height of the blades must be increased so as to increase the volume of air draw into the apparatus. This interferes with efforts to make the fan apparatus thinner.
FIG. 7A is a perspective view of a fan blade assembly of a conventional axial fan blade type. FIG. 7B is a cross-sectional front view of a portion of a fan apparatus having the fan blade assembly of the axial fan blade type.
A plurality of axial fan blades 22 are formed around a peripheral portion of a rotor 20 fitted on a shaft 21. The fan blade assembly is housed in a thin housing 24. Air is drawn in from the axial direction and is discharged perpendicular to the axial direction. In this case, however, there is significant air backflow after the air hits a bottom portion of the housing 24. This results in ineffective airflow toward the periphery of the blades, reducing the efficiency of discharge to the outlet 23a.
FIG. 8A is a perspective view of a fan blade assembly of a centrifugal fan blade type. FIG. 8B is a cross-sectional front view of a portion of a fan apparatus having a blade assembly of the centrifugal fan blade type.
As shown in FIG. 8A, a plurality of centrifugal blades 27 are formed on a peripheral portion of a rotor 29 fitted on a shaft 26. The fan blade assembly is housed in a thin housing 28. Air is drawn in from the axial direction and is discharged perpendicular to the axial direction. In this case, the air which is drawn in flows toward the periphery of the blades; however, unlike the case of the axial fan blade, the drawing in of air is ineffective. The volume of air to be drawn in is determined by the height of the blades; therefore, the volume of air to be discharged from an outlet 28 cannot be increased.